Rach resource selection

ABSTRACT

A UE may obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO. The UE may evaluate the multiple qualifying SSBs/CSI-RSs and select one SSB/CSI-RS among the qualifying SSBs/CSI-RSs based on a scheduling opportunity of the associated ROs and a power usage on the UE side.

TECHNICAL FIELD

The present disclosure relates generally to communication systems, and more particularly, to a method of wireless communication including a random access channel (RACH) selection.

INTRODUCTION

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR). 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT)), and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

BRIEF SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects. This summary neither identifies key or critical elements of all aspects nor delineates the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may include a user equipment (UE) configured to obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first random access channel (RACH) occasion (RO) associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

FIG. 2A is a diagram illustrating an example of a first frame, in accordance with various aspects of the present disclosure.

FIG. 2B is a diagram illustrating an example of DL channels within a subframe, in accordance with various aspects of the present disclosure.

FIG. 2C is a diagram illustrating an example of a second frame, in accordance with various aspects of the present disclosure.

FIG. 2D is a diagram illustrating an example of UL channels within a subframe, in accordance with various aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example of a base station and user equipment (UE) in an access network.

FIG. 4 shows an example of selecting a RACH resource.

FIG. 5 is a flowchart of an example of selecting a RACH resource.

FIG. 6 is a call-flow diagram of a method of wireless communication.

FIG. 7 is a flowchart of a method of wireless communication.

FIG. 8 is a flowchart of a method of wireless communication.

FIG. 9 is a diagram illustrating an example of a hardware implementation for an example apparatus and/or network entity.

DETAILED DESCRIPTION

The UE may initiate the RACH procedure, and detect multiple qualifying SSBs/CSI-RSs that meet the metric threshold value. In some cases, selecting the strongest SSB/CSI-RS associated with RO with a relatively longer time distance from the current time may cause increased network latency. Based on the implementation of the current disclosure, the UE may evaluate the multiple qualifying SSBs/CSI-RSs and select one SSB/CSI-RS among the qualifying SSBs/CSI-RSs based on a scheduling opportunity of the associated ROs and a power usage on the UE side.

The detailed description set forth below in connection with the drawings describes various configurations and does not represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems are presented with reference to various apparatus and methods. These apparatus and methods are described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise, shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, or any combination thereof.

Accordingly, in one or more example aspects, implementations, and/or use cases, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, such computer-readable media can comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

While aspects, implementations, and/or use cases are described in this application by illustration to some examples, additional or different aspects, implementations and/or use cases may come about in many different arrangements and scenarios. Aspects, implementations, and/or use cases described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, and packaging arrangements. For example, aspects, implementations, and/or use cases may come about via integrated chip implementations and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, artificial intelligence (AI)-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described examples may occur. Aspects, implementations, and/or use cases may range a spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or original equipment manufacturer (OEM) devices or systems incorporating one or more techniques herein. In some practical settings, devices incorporating described aspects and features may also include additional components and features for implementation and practice of claimed and described aspect. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders/summers, etc.). Techniques described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, aggregated or disaggregated components, end-user devices, etc. of varying sizes, shapes, and constitution.

Deployment of communication systems, such as 5G NR systems, may be arranged in multiple manners with various components or constituent parts. In a 5G NR system, or network, a network node, a network entity, a mobility element of a network, a radio access network (RAN) node, a core network node, a network element, or a network equipment, such as a base station (BS), or one or more units (or one or more components) performing base station functionality, may be implemented in an aggregated or disaggregated architecture. For example, a BS (such as a Node B (NB), evolved NB (eNB), NR BS, 5G NB, access point (AP), a transmit receive point (TRP), or a cell, etc.) may be implemented as an aggregated base station (also known as a standalone BS or a monolithic BS) or a disaggregated base station.

An aggregated base station may be configured to utilize a radio protocol stack that is physically or logically integrated within a single RAN node. A disaggregated base station may be configured to utilize a protocol stack that is physically or logically distributed among two or more units (such as one or more central or centralized units (CUs), one or more distributed units (DUs), or one or more radio units (RUs)). In some aspects, a CU may be implemented within a RAN node, and one or more DUs may be co-located with the CU, or alternatively, may be geographically or virtually distributed throughout one or multiple other RAN nodes. The DUs may be implemented to communicate with one or more RUs. Each of the CU, DU and RU can be implemented as virtual units, i.e., a virtual central unit (VCU), a virtual distributed unit (VDU), or a virtual radio unit (VRU).

Base station operation or network design may consider aggregation characteristics of base station functionality. For example, disaggregated base stations may be utilized in an integrated access backhaul (IAB) network, an open radio access network (O-RAN (such as the network configuration sponsored by the O-RAN Alliance)), or a virtualized radio access network (vRAN, also known as a cloud radio access network (C-RAN)). Disaggregation may include distributing functionality across two or more units at various physical locations, as well as distributing functionality for at least one unit virtually, which can enable flexibility in network design. The various units of the disaggregated base station, or disaggregated RAN architecture, can be configured for wired or wireless communication with at least one other unit.

FIG. 1 is a diagram 100 illustrating an example of a wireless communications system and an access network. The illustrated wireless communications system includes a disaggregated base station architecture. The disaggregated base station architecture may include one or more CUs 110 that can communicate directly with a core network 120 via a backhaul link, or indirectly with the core network 120 through one or more disaggregated base station units (such as a Near-Real Time (Near-RT) RAN Intelligent Controller (RIC) 125 via an E2 link, or a Non-Real Time (Non-RT) RIC 115 associated with a Service Management and Orchestration (SMO) Framework 105, or both). A CU 110 may communicate with one or more DUs 130 via respective midhaul links, such as an F1 interface. The DUs 130 may communicate with one or more RUs 140 via respective fronthaul links. The RUs 140 may communicate with respective UEs 104 via one or more radio frequency (RF) access links. In some implementations, the UE 104 may be simultaneously served by multiple RUs 140.

Each of the units, i.e., the CUs 110, the DUs 130, the RUs 140, as well as the Near-RT RICs 125, the Non-RT RICs 115, and the SMO Framework 105, may include one or more interfaces or be coupled to one or more interfaces configured to receive or to transmit signals, data, or information (collectively, signals) via a wired or wireless transmission medium. Each of the units, or an associated processor or controller providing instructions to the communication interfaces of the units, can be configured to communicate with one or more of the other units via the transmission medium. For example, the units can include a wired interface configured to receive or to transmit signals over a wired transmission medium to one or more of the other units. Additionally, the units can include a wireless interface, which may include a receiver, a transmitter, or a transceiver (such as an RF transceiver), configured to receive or to transmit signals, or both, over a wireless transmission medium to one or more of the other units.

In some aspects, the CU 110 may host one or more higher layer control functions. Such control functions can include radio resource control (RRC), packet data convergence protocol (PDCP), service data adaptation protocol (SDAP), or the like. Each control function can be implemented with an interface configured to communicate signals with other control functions hosted by the CU 110. The CU 110 may be configured to handle user plane functionality (i.e., Central Unit—User Plane (CU-UP)), control plane functionality (i.e., Central Unit—Control Plane (CU-CP)), or a combination thereof. In some implementations, the CU 110 can be logically split into one or more CU-UP units and one or more CU-CP units. The CU-UP unit can communicate bidirectionally with the CU-CP unit via an interface, such as an E1 interface when implemented in an O-RAN configuration. The CU 110 can be implemented to communicate with the DU 130, as necessary, for network control and signaling.

The DU 130 may correspond to a logical unit that includes one or more base station functions to control the operation of one or more RUs 140. In some aspects, the DU 130 may host one or more of a radio link control (RLC) layer, a medium access control (MAC) layer, and one or more high physical (PHY) layers (such as modules for forward error correction (FEC) encoding and decoding, scrambling, modulation, demodulation, or the like) depending, at least in part, on a functional split, such as those defined by 3GPP. In some aspects, the DU 130 may further host one or more low PHY layers. Each layer (or module) can be implemented with an interface configured to communicate signals with other layers (and modules) hosted by the DU 130, or with the control functions hosted by the CU 110.

Lower-layer functionality can be implemented by one or more RUs 140. In some deployments, an RU 140, controlled by a DU 130, may correspond to a logical node that hosts RF processing functions, or low-PHY layer functions (such as performing fast Fourier transform (FFT), inverse FFT (iFFT), digital beamforming, physical random access channel (PRACH) extraction and filtering, or the like), or both, based at least in part on the functional split, such as a lower layer functional split. In such an architecture, the RU(s) 140 can be implemented to handle over the air (OTA) communication with one or more UEs 104. In some implementations, real-time and non-real-time aspects of control and user plane communication with the RU(s) 140 can be controlled by the corresponding DU 130. In some scenarios, this configuration can enable the DU(s) 130 and the CU 110 to be implemented in a cloud-based RAN architecture, such as a vRAN architecture.

The SMO Framework 105 may be configured to support RAN deployment and provisioning of non-virtualized and virtualized network elements. For non-virtualized network elements, the SMO Framework 105 may be configured to support the deployment of dedicated physical resources for RAN coverage requirements that may be managed via an operations and maintenance interface (such as an O1 interface). For virtualized network elements, the SMO Framework 105 may be configured to interact with a cloud computing platform (such as an open cloud (O-Cloud) 190 to perform network element life cycle management (such as to instantiate virtualized network elements) via a cloud computing platform interface (such as an O2 interface). Such virtualized network elements can include, but are not limited to, CUs 110, DUs 130, RUs 140 and Near-RT RICs 125. In some implementations, the SMO Framework 105 can communicate with a hardware aspect of a 4G RAN, such as an open eNB (O-eNB) 111, via an O1 interface. Additionally, in some implementations, the SMO Framework 105 can communicate directly with one or more RUs 140 via an O1 interface. The SMO Framework 105 also may include a Non-RT RIC 115 configured to support functionality of the SMO Framework 105.

The Non-RT RIC 115 may be configured to include a logical function that enables non-real-time control and optimization of RAN elements and resources, artificial intelligence (AI)/machine learning (ML) (AI/ML) workflows including model training and updates, or policy-based guidance of applications/features in the Near-RT RIC 125. The Non-RT RIC 115 may be coupled to or communicate with (such as via an A1 interface) the Near-RT RIC 125. The Near-RT RIC 125 may be configured to include a logical function that enables near-real-time control and optimization of RAN elements and resources via data collection and actions over an interface (such as via an E2 interface) connecting one or more CUs 110, one or more DUs 130, or both, as well as an O-eNB, with the Near-RT RIC 125.

In some implementations, to generate AI/ML models to be deployed in the Near-RT RIC 125, the Non-RT RIC 115 may receive parameters or external enrichment information from external servers. Such information may be utilized by the Near-RT RIC 125 and may be received at the SMO Framework 105 or the Non-RT RIC 115 from non-network data sources or from network functions. In some examples, the Non-RT RIC 115 or the Near-RT RIC 125 may be configured to tune RAN behavior or performance. For example, the Non-RT RIC 115 may monitor long-term trends and patterns for performance and employ AI/ML models to perform corrective actions through the SMO Framework 105 (such as reconfiguration via O1) or via creation of RAN management policies (such as A1 policies).

At least one of the CU 110, the DU 130, and the RU 140 may be referred to as a base station 102. Accordingly, a base station 102 may include one or more of the CU 110, the DU 130, and the RU 140 (each component indicated with dotted lines to signify that each component may or may not be included in the base station 102). The base station 102 provides an access point to the core network 120 for a UE 104. The base stations 102 may include macrocells (high power cellular base station) and/or small cells (low power cellular base station). The small cells include femtocells, picocells, and microcells. A network that includes both small cell and macrocells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG). The communication links between the RUs 140 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to an RU 140 and/or downlink (DL) (also referred to as forward link) transmissions from an RU 140 to a UE 104. The communication links may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102/UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL than for UL). The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell).

Certain UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 may use the DL/UL wireless wide area network (WWAN) spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be through a variety of wireless D2D communications systems, such as for example, Bluetooth, Wi-Fi based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.

The wireless communications system may further include a Wi-Fi AP 150 in communication with UEs 104 (also referred to as Wi-Fi stations (STAs)) via communication link 154, e.g., in a 5 GHz unlicensed frequency spectrum or the like. When communicating in an unlicensed frequency spectrum, the UEs 104/AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

The electromagnetic spectrum is often subdivided, based on frequency/wavelength, into various classes, bands, channels, etc. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz-7.125 GHz) and FR2 (24.25 GHz-52.6 GHz). Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz-300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Recent 5G NR studies have identified an operating band for these mid-band frequencies as frequency range designation FR3 (7.125 GHz-24.25 GHz). Frequency bands falling within FR3 may inherit FR1 characteristics and/or FR2 characteristics, and thus may effectively extend features of FR1 and/or FR2 into mid-band frequencies. In addition, higher frequency bands are currently being explored to extend 5G NR operation beyond 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR2-2 (52.6 GHz-71 GHz), FR4 (71 GHz-114.25 GHz), and FR5 (114.25 GHz-300 GHz). Each of these higher frequency bands falls within the EHF band.

With the above aspects in mind, unless specifically stated otherwise, the term “sub-6 GHz” or the like if used herein may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, the term “millimeter wave” or the like if used herein may broadly represent frequencies that may include mid-band frequencies, may be within FR2, FR4, FR2-2, and/or FR5, or may be within the EHF band.

The base station 102 and the UE 104 may each include a plurality of antennas, such as antenna elements, antenna panels, and/or antenna arrays to facilitate beamforming. The base station 102 may transmit a beamformed signal 182 to the UE 104 in one or more transmit directions. The UE 104 may receive the beamformed signal from the base station 102 in one or more receive directions. The UE 104 may also transmit a beamformed signal 184 to the base station 102 in one or more transmit directions. The base station 102 may receive the beamformed signal from the UE 104 in one or more receive directions. The base station 102/UE 104 may perform beam training to determine the best receive and transmit directions for each of the base station 102/UE 104. The transmit and receive directions for the base station 102 may or may not be the same. The transmit and receive directions for the UE 104 may or may not be the same.

The base station 102 may include and/or be referred to as a gNB, Node B, eNB, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit reception point (TRP), network node, network entity, network equipment, or some other suitable terminology. The base station 102 can be implemented as an integrated access and backhaul (IAB) node, a relay node, a sidelink node, an aggregated (monolithic) base station with a baseband unit (BBU) (including a CU and a DU) and an RU, or as a disaggregated base station including one or more of a CU, a DU, and/or an RU. The set of base stations, which may include disaggregated base stations and/or aggregated base stations, may be referred to as next generation (NG) RAN (NG-RAN).

The core network 120 may include an Access and Mobility Management Function (AMF) 161, a Session Management Function (SMF) 162, a User Plane Function (UPF) 163, a Unified Data Management (UDM) 164, one or more location servers 168, and other functional entities. The AMF 161 is the control node that processes the signaling between the UEs 104 and the core network 120. The AMF 161 supports registration management, connection management, mobility management, and other functions. The SMF 162 supports session management and other functions. The UPF 163 supports packet routing, packet forwarding, and other functions. The UDM 164 supports the generation of authentication and key agreement (AKA) credentials, user identification handling, access authorization, and subscription management. The one or more location servers 168 are illustrated as including a Gateway Mobile Location Center (GMLC) 165 and a Location Management Function (LMF) 166. However, generally, the one or more location servers 168 may include one or more location/positioning servers, which may include one or more of the GMLC 165, the LMF 166, a position determination entity (PDE), a serving mobile location center (SMLC), a mobile positioning center (MPC), or the like. The GMLC 165 and the LMF 166 support UE location services. The GMLC 165 provides an interface for clients/applications (e.g., emergency services) for accessing UE positioning information. The LMF 166 receives measurements and assistance information from the NG-RAN and the UE 104 via the AMF 161 to compute the position of the UE 104. The NG-RAN may utilize one or more positioning methods in order to determine the position of the UE 104. Positioning the UE 104 may involve signal measurements, a position estimate, and an optional velocity computation based on the measurements. The signal measurements may be made by the UE 104 and/or the serving base station 102. The signals measured may be based on one or more of a satellite positioning system (SPS) 170 (e.g., one or more of a Global Navigation Satellite System (GNSS), global position system (GPS), non-terrestrial network (NTN), or other satellite position/location system), LTE signals, wireless local area network (WLAN) signals, Bluetooth signals, a terrestrial beacon system (TBS), sensor-based information (e.g., barometric pressure sensor, motion sensor), NR enhanced cell ID (NR E-CID) methods, NR signals (e.g., multi-round trip time (Multi-RTT), DL angle-of-departure (DL-AoD), DL time difference of arrival (DL-TDOA), UL time difference of arrival (UL-TDOA), and UL angle-of-arrival (UL-AoA) positioning), and/or other systems/signals/sensors.

Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or any other similar functioning device. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, etc.). The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. In some scenarios, the term UE may also apply to one or more companion devices such as in a device constellation arrangement. One or more of these devices may collectively access the network and/or individually access the network.

Referring again to FIG. 1 , in certain aspects, the UE 104 may include a RACH resource selecting component 198 configured to obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO. Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

FIG. 2A is a diagram 200 illustrating an example of a first subframe within a 5G NR frame structure. FIG. 2B is a diagram 230 illustrating an example of DL channels within a 5G NR subframe. FIG. 2C is a diagram 250 illustrating an example of a second subframe within a 5G NR frame structure. FIG. 2D is a diagram 280 illustrating an example of UL channels within a 5G NR subframe. The 5G NR frame structure may be frequency division duplexed (FDD) in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for either DL or UL, or may be time division duplexed (TDD) in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for both DL and UL. In the examples provided by FIGS. 2A, 2C, the 5G NR frame structure is assumed to be TDD, with subframe 4 being configured with slot format 28 (with mostly DL), where D is DL, U is UL, and F is flexible for use between DL/UL, and subframe 3 being configured with slot format 1 (with all UL). While subframes 3, 4 are shown with slot formats 1, 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. UEs are configured with the slot format (dynamically through DL control information (DCI), or semi-statically/statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI). Note that the description infra applies also to a 5G NR frame structure that is TDD.

FIGS. 2A-2D illustrate a frame structure, and the aspects of the present disclosure may be applicable to other wireless communication technologies, which may have a different frame structure and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. Each slot may include 14 or 12 symbols, depending on whether the cyclic prefix (CP) is normal or extended. For normal CP, each slot may include 14 symbols, and for extended CP, each slot may include 12 symbols. The symbols on DL may be CP orthogonal frequency division multiplexing (OFDM) (CP-OFDM) symbols. The symbols on UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also referred to as single carrier frequency-division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to a single stream transmission). The number of slots within a subframe is based on the CP and the numerology. The numerology defines the subcarrier spacing (SCS) and, effectively, the symbol length/duration, which is equal to 1/SCS.

μ SCS Δf = 2^(μ) · 15[kHz] Cyclic prefix 0 15 Normal 1 30 Normal 2 60 Normal, Extended 3 120 Normal 4 240 Normal

For normal CP (14 symbols/slot), different numerologies μ 0 to 4 allow for 1, 2, 4, 8, and 16 slots, respectively, per subframe. For extended CP, the numerology 2 allows for 4 slots per subframe. Accordingly, for normal CP and numerology μ, there are 14 symbols/slot and 2^(μ) slots/subframe. The subcarrier spacing may be equal to 2^(μ)* 15 kHz, where μ is the numerology 0 to 4. As such, the numerology μ=0 has a subcarrier spacing of 15 kHz and the numerology μ=4 has a subcarrier spacing of 240 kHz. The symbol length/duration is inversely related to the subcarrier spacing. FIGS. 2A-2D provide an example of normal CP with 14 symbols per slot and numerology μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs. Within a set of frames, there may be one or more different bandwidth parts (BWPs) (see FIG. 2B) that are frequency division multiplexed. Each BWP may have a particular numerology and CP (normal or extended).

A resource grid may be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as physical RBs (PRBs)) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include demodulation RS (DM-RS) (indicated as R for one particular configuration, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS may also include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS).

FIG. 2B illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) (e.g., 1, 2, 4, 8, or 16 CCEs), each CCE including six RE groups (REGs), each REG including 12 consecutive REs in an OFDM symbol of an RB. A PDCCH within one BWP may be referred to as a control resource set (CORESET). A UE is configured to monitor PDCCH candidates in a PDCCH search space (e.g., common search space, UE-specific search space) during PDCCH monitoring occasions on the CORESET, where the PDCCH candidates have different DCI formats and different aggregation levels. Additional BWPs may be located at greater and/or lower frequencies across the channel bandwidth. A primary synchronization signal (PSS) may be within symbol 2 of particular subframes of a frame. The PSS is used by a UE 104 to determine subframe/symbol timing and a physical layer identity. A secondary synchronization signal (SSS) may be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the DM-RS. The physical broadcast channel (PBCH), which carries a master information block (MIB), may be logically grouped with the PSS and SSS to form a synchronization signal (SS)/PBCH block (also referred to as SS block (SSB)). The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and depending on the particular PUCCH format used. The UE may transmit sounding reference signals (SRS). The SRS may be transmitted in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

FIG. 2D illustrates an example of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and hybrid automatic repeat request (HARQ) acknowledgment (ACK) (HARQ-ACK) feedback (i.e., one or more HARQ ACK bits indicating one or more ACK and/or negative ACK (NACK)). The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of a base station 310 in communication with a UE 350 in an access network. In the DL, Internet protocol (IP) packets may be provided to a controller/processor 375. The controller/processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression/decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318Tx. Each transmitter 318Tx may modulate a radio frequency (RF) carrier with a respective spatial stream for transmission.

At the UE 350, each receiver 354Rx receives a signal through its respective antenna 352. Each receiver 354Rx recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions may be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to the controller/processor 359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets. The controller/processor 359 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DL transmission by the base station 310, the controller/processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression/decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a reference signal or feedback transmitted by the base station 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antenna 352 via separate transmitters 354Tx. Each transmitter 354Tx may modulate an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318Rx receives a signal through its respective antenna 320. Each receiver 318Rx recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets. The controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

At least one of the TX processor 368, the RX processor 356, and the controller/processor 359 may be configured to perform aspects in connection with the RACH resource selecting component 198 198 of FIG. 1 .

In some aspects, a UE may initiate a RACH procedure to establish an RRC connection and communicate data transmissions with a wireless network including a network node (e.g., gNB, base station, AP, TRP, etc.). The UE initiating the RACH procedure may receive a set of SSBs/CSI-RSs associated with a set of PRACH resources from the network node. Here, the PRACH resource may be used as a generic term to refer to either SSB or CSI-RS resources selected for Msg1 transmission. That is, the PRACH resource may be associated with a target SSB/CSI-RS selected by the UE, and the UE may select the PRACH resource to transmit the Msg1 based on at least one quality of the target SSB/CSI-RS. Here, the target SSB/CSI-RS may refer to the SSB/CSI-RS that the UE selects from the set of SSB/CSI-RS based on the respective metrics, and the PRACH resource may be associated with the target SSB/CSI-RS. The UE may select the target SSB/CSI-RS from the set of SSBs/CSI-RSs based at least in part on a metric of the SSBs/CSI-RSs. For example, the metric may include reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-noise ratio (SNR), or signal-to-interference plus noise ratio (SINR). In one example, the UE may select the SSB/CSI-RS for the RACH procedure based on the highest quality, based at least in part on a RSRP measurement. In another example, the lower layer of the UE may measure all available SSBs/CSI-RSs, and select the SSB/CSI-RS with the highest RSRP and initiate the RACH procedure using the selected SSB/CSI-RS.

In the RACH procedure, all RACH occasions (ROs) in the time-frequency domains may be mapped to some amount of SSB/CSI-RS resources in order to transmit a Msg1. That is, each SSB of the set of SSBs may be associated with one RO of a set of ROs. Here, the RO may refer to a time/frequency instance (or a set of time/frequency resources) in which the UE may transmit the Msg1. Here, Msg1 may refer to the RACH message including the PRACH preamble which may be transmitted by the UE to the network node.

In some aspects, the UE may detect multiple SSBs/CSI-RSs satisfying SSB/CSI-RS-threshold criteria, and the multiple SSBs/CSI-RSs may be available or qualifying for the UE to select for the RACH procedure. That is, the UE may be configured to determine that one or more SSBs/CSI-RSs may be available to perform the RACH procedure based on the at least one metric of the one or more SSBs/CSI-RSs being above a threshold value (e.g., a qualifying metric). Here, the one or more SSBs/CSI-RSs with the metrics higher than the qualifying metric may be referred to as qualifying resources. The UE may identify a set of qualifying resources including a subset of SSBs/CSI-RSs, among the set of SSBs/CSI-RSs, having metrics higher than the qualifying metric. The UE may be configured with at least one implementation to select one SSB/CSI-RS, among the set of qualifying resources satisfying the SSB/CSI-RS threshold criteria, for the RACH procedure. In one example, the UE may select the SSB/CSI-RS with the highest metric measured and select the RO associated with the selected SSB/CSI-RS having the highest quality (e.g., metric) measured to perform the RACH procedure.

In one aspect, the UE may select the target SSB/CSI-RS for RACH based on the highest quality measured, e.g., the RSRP. That is, the UE may be implemented with a lower layer to measure all available SSBs/CSI-RSs, e.g., associated with SSBs/CSI-RSs, and select the SSB/CSI-RS with the highest RSRP, and perform the RACH procedure on the selected SSB/CSI-RS. In some examples, depending on the RACH configuration and SSB/CSI-RS selection, the next available RO associated with the selected SSB/CSI-RS may be relatively far in time domain from the current time, e.g., over 10-15 frames (100-150 ms). The time distance from the current time to the next available RO associated with the selected SSB/CSI-RS may cause a relatively long delay for the UE to establish and/or maintain a connection, e.g., the RRC connection, with the network.

In one example, a UE may be associated with a network configuration of FR1 TDD, and the network node may configure the UE with a PRACH-configuration index of 191. Here, the PRACH-configuration index of 191 may indicate a set of PRACH configurations as provided in the following table.

Number of time- domain Number of PRACH PRACH occasion PRACH slots within a Config Preamble n_(SFN) mod x = y Subframe Starting within a PRACH PRACH Index format x y number symbol subframe slot duration 191 C2 4 1 9 2 1 2 6

Based on the PRACH confirmation, the UE may understand that two (2) ROs are available in one frame and every four (4) frames, starting from frame 1. In one example, the number of transmitted SSBs may be six (6), the number of SSBs mapped to each RO may be one (1), and the selected RACH SSB (e.g., target RACH) may be SSB ID 0. Because two ROs are available every four frames, each RO mapped to one SSB of total six SSBs, the following set of frames may include the corresponding SSBs:

PRACH configuration period index Frame number (e.g., SFN) (SSB IDs) 0 01 (0, 1) 05 (2, 3) 09 (4, 5) 13 (invalid) 1 17 (0, 1) 21 (2, 3) 25 (4, 5) 29 (invalid) 2 33 (0, 1) 37 (2, 3) 41 (4, 5) 45 (invalid) 4 49 (0, 1) 53 (2, 3) 57 (4, 5) 61 (invalid) . . . . . . . . . . . . . . .

For example, the current frame that the UE is scheduling the RACH Msg1 may be associated with an SFN 34. Accordingly, if the current frame is SFN34 and the next available RO corresponding to SSB ID 0 is SFN 49, the UE may wait 15 frames (e.g., 150 ms) to transmit the Msg1.

In one aspect, the second SSB, e.g., corresponding to SSB ID 2, may be another qualifying resource with its metric higher than the qualifying metric (e.g., the threshold value) and smaller than the metric of the SSB ID 0. In one example, the UE may be configured to select the SSB ID 2, which is a qualifying resource, to perform the RACH procedure. Accordingly, the UE may select SSB ID 2 rather than SSB ID 0 at the current frame (e.g., SFN34), and the next available RO corresponding to the SSB ID 2 is SFN37, and the UE may transmit the Msg1 with a reduced network latency and an improved efficiency. That is, the UE may reduce the latency in transmitting the Msg1 from 15 frames (e.g., 150 ms) to 3 frames (e.g., 30 ms) by selecting the SSB ID 2, which is a qualifying resource with less than a greatest metric among the qualifying resources, rather than the SSB ID 0 with the greatest metric among the qualifying resources.

In some aspects, the UE may include a method of PRACH resource selection including a reduced network latency. The UE may select the RACH resource with increased flexibility for the PRACH scheduling, and the UE may improve the efficiency or optimize the flow of the RACH procedure by adding logic to further select between the qualifying resources based on the mapping between the PRACH resource and the RO. The UE may enhance the resource selection algorithm to consider a preferred set of qualifying resources, rather than selecting the strongest SSB/CSI-RS, e.g., the SSB/CSI-RS with the greatest metric. Accordingly, the UE may be implemented to determine which resource is mapped to the nearest RO relative to the current system time, and reduce or minimize the delay between the RACH procedure trigger point (e.g., the current time) and the Msg1 transmission, or between subsequent Msg1 retransmissions. Also, in order to minimize or reduce unwanted power consumption impact from the implementation, the UE may select resources within an acceptable threshold of quality in comparison to the strongest resource available.

The UE may determine the PRACH resource from the set of PRACH resources based on at least one metric of the PRACH resource and the RO associated with the PRACH resource. That is, the UE may select the PRACH resource for transmitting the Msg1 to the network node based on the at least one metric of the PRACH resource and a time distance of a RO associated with the PRACH resource from the current system time.

FIG. 4 shows an example of selecting a RACH resource from a set of qualifying resources 400. The qualifying resources 400 may include first SSB/CSI-RS 402, second SSB/CSI-RS 404, third SSB/CSI-RS 406, and fourth SSB/CSI-RS 408. In some aspects, the UE may select the RACH resource based on a scheduling opportunity and a power usage.

Referring to FIG. 4 , multiple SSB/CSI-RS resources may meet the RSRP threshold specification. The multiple SSB/CSI-RS resources meeting the RSRP threshold specification may be referred as a set of qualifying resources 400, and each SSB/CSI-RS resource of the set of qualifying resources 400 may have a metric above a threshold value (e.g., the qualifying metric). Here, the set of qualifying resources 400 may be a subset of the set of SSB/CSI-RS resources. The UE may select one SSB among the set of qualifying resources 400 and the RO mapped to the selected SSB may have a time distance from the current time 420 and effect on UE power consumption. In one example, the UE may select the resource mapped to the closest RO mapped to a suboptimal SSB/CSI-RS. The RO mapped to the selected SSB may have a relatively shorter time distance from the current time 420, and may cause an increased power consumption to transmit the Msg1 on the UE's side due to the relatively lower signal power. In another example, the SSB may select the SSB with the highest metric (e.g., the best SSB/CSI-RS), regardless of the RO mapped to the selected SSB. The RO mapped to the selected SSB may have a relatively higher channel metric and reduce the power consumption on the UE's side, and the RO mapped to the selected SSB may have a relatively longer time distance from the current time 420, increasing the network latency to transmit the Msg1.

In some aspects, the UE may evaluate the set of qualifying SSBs/CSI-RSs and select a resource which may balance the power usage on the UE's side and the time distance from the current time to the corresponding RO.

In one aspect, the UE may analyze the transmit power difference between each qualifying resource and the strongest resource. In one example, the UE may analyze whether the delta transmit power difference, e.g., between the best resource and the other qualifying resources, is within the remaining UE power budget for the RACH procedure. To analyze the transmit power difference, the UE may define a second threshold (e.g., a power threshold) to compare each resource with the strongest SSB with respect to the RSRP or the SNR measurements. That is, the UE may compare the RSRP or the SNR metric of each qualifying SSB with the strongest SSB/CSI-RS, e.g., the qualifying SSB with the highest RSRP measurement. The UE may identify a subset of the qualifying SSBs that has the difference in the RSRP or the SNR metric with the strongest resource within the second threshold (e.g., the power threshold), then the UE may select a PRACH resource from the subset of qualifying resources. Here, the subset of qualifying resources within the power threshold may be called a cluster. The UE may select the PRACH resource having the most optimal RO scheduling opportunity from the cluster, e.g., the subset of qualifying resources within the power threshold. In one aspect, the power threshold may be configured by the network node.

In another aspect, the UE may analyze the RO time distance for each qualifying resource of the cluster (e.g., the subset of qualifying resources) compared to the strongest resource. That is, the UE may calculate the time distance for each qualifying resources of the cluster from the current time 420, and select the qualifying resource with the shortest time distance (or the smallest time difference) from the current time 420 as the PRACH resource.

Referring to set of qualifying resources 400, the UE may obtain the set of qualifying resources 400 from a set of SSB resources based on a RSRP threshold (e.g., the first threshold). Here, the RSRP threshold may be −80 dBm, and the UE may obtain the set of qualifying resources 400 (e.g., the subset of the SSB resources) including the first SSB/CSI-RS 402, the second SSB/CSI-RS 404, the third SSB/CSI-RS 406, and the fourth SSB/CSI-RS 408, because the SSB0 has a RSRP measurement of −70 dBm, the SSB1 has a RSRP measurement of −72 dBm, the SSB2 has a RSRP measurement of −79 dBm, and the SSB3 has a RSRP measurement of −73 dBm. Accordingly, the first SSB/CSI-RS 402 may be determined the strongest SSB/CSI-RS, and the UE may compare the other SSBs/CSI-RSs with the first SSB/CSI-RS 402 to identify the cluster 410 (e.g., the subset of qualifying resources that meets the power threshold).

The UE may be configured with the power threshold (e.g., the second threshold) of 3 dBm. Therefore, the UE may compare the second SSB/CSI-RS 404, the third SSB/CSI-RS 406, and the fourth SSB/CSI-RS 408 with the strongest SSB/CSI-RS, e.g., the first SSB/CSI-RS 402, and identify that the cluster 410 may meet the power threshold of 3 dBm. That is, the UE may determine that the second SSB/CSI-RS 404 and the fourth SSB/CSI-RS 408 have the RSRP measurement of −72 dBm and −73 dBm, that have the difference in the RSRP or the SNR metric less than or equal to 3 dBm from the RSRP measurement of the strongest SSB/CSI-RS (−70 dBm of the SSB0). The UE may also determine that the difference in the RSRP measurement of the third SSB/CSI-RS 406 from the first SSB/CSI-RS 402 is 9 dBm, which is greater than the power threshold, e.g., 3 dBm. The UE may identify that the cluster 410 includes the SSB0, the second SSB/CSI-RS 404, and the fourth SSB/CSI-RS 408.

Even if the third SSB/CSI-RS 406 is closest to the current time 420 (e.g., has the smallest time difference from the current time 420) among the set of qualifying resources 400, the UE may disregard the third SSB/CSI-RS 406 from selecting the PRACH resource because the quality of the SSB/CSI-RS may be deemed too poor and the scheduling advantage may be outweighed by the power consumption trade-off.

The UE may further evaluate each SSB of the cluster 410 including the SSB0, the second SSB/CSI-RS 404, and the fourth SSB/CSI-RS 408, and determine the PRACH resource that is associated with a RO that has the smallest time difference from the current time 420 in the time domain. For example, the SSB3 is the closest to the current time 420 (e.g., has the smallest time difference from the current time 420) among the cluster 410, the UE may select the SSB3 as the PRACH resource, and transmit the Msg1 including the RACH preamble to the network node.

FIG. 5 is a flowchart 500 of an example of selecting a PRACH resource. At 502, the RACH procedure may be triggered and the UE may begin the resource selection step. That is, the UE may start measuring available PRACH resource (i.e. SSB or CSI-RS) (e.g., based on a set of SSBs/CSI-RSs available on the UE side).

At 504, based on the measurements of the available SSBs/CSI-RSs, the UE may find a subset of available resources (e.g., SSBs/CSI-RSs) that may satisfy a first threshold. Here, the first threshold may be the RSRP threshold, and the subset of available resources may be referred to as the qualifying resources.

At 506, the UE may filter down the qualifying resources to a subset of the qualifying resources which meet the power threshold. That is, the UE may first identify the best resource, e.g., the best SSB/CSI-RS or the strongest resource with the highest metric among the set of the qualifying resources, and compare each qualifying resource to the best resource. The UE may identify a cluster, e.g., a subset of the qualifying resources having the difference in power with respect to the best resource that is smaller than or equal to the power threshold.

At 510, in one aspect, the UE may determine that more than one resource may be included in the cluster. Then the UE may, at 512, evaluate each qualifying resource in the cluster to determine the qualifying resource mapped to the next earliest RO time with respect to the current time. At 514, the UE may select the qualifying resource in the cluster mapped to the next earliest RO time with respect to the current time as the PRACH resource.

At 520, in another aspect, the UE may determine that no qualifying resources meet the power threshold criterial. That is, the UE may compare each qualifying resource to the best resource, and determine all the qualifying resources have differences in power with respect to the best resource that is greater than the power threshold. Accordingly, the cluster includes the best resource. At 522, the UE may select the best resource as the PRACH resource.

At 530, the UE may transmit the Msg 1 with the selected PRACH resource. The PRACH resource may be the qualifying resource in the cluster mapped to the next earliest RO time with respect to the current time selected at 514 or the best resource selected at 522.

FIG. 6 is a call-flow diagram 600 of a method of wireless communication. The call-flow diagram 600 may include a UE 602 and a network node 604. The UE 602 may evaluate the multiple qualifying SSBs/CSI-RSs and select one SSB/CSI-RS among the qualifying SSBs/CSI-RSs based on a scheduling opportunity of the associated ROs and a power usage on the UE side. The UE 602 may obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node 604 in the first RO. Here, the set of channel metrics of a PRACH resource may refer to at least one of a quality or a measurement of the PRACH resource, e.g., the RSRP, RSRQ, SNR, SINR, etc.

At 606, the UE 602 may trigger a RACH procedure. The triggering of the RACH procedure may be based on various scenarios including initial access procedure, a radio link failure, etc. Based on triggering the RACH procedure, the UE 602 may obtain a first subset of PRACH resources from a set of PRACH resources at 620. Here, the set of PRACH resources may include a set of SSBs or a set of CSI-RSs.

At 608, the UE 602 may receive a second indication of the second threshold value. Here, the second threshold value may be a power threshold for the UE 602 to determine a second set of PRACH resources (e.g., a cluster 410) of PRACH resources that meets the power threshold, at 636.

At 610, the UE 602 may measure the set of channel metrics of the set of PRACH resources. In one example, the set of channel metrics of each PRACH resource of the first subset of PRACH resources may include an RSRP or an SNR of each PRACH resource of the first subset of PRACH resources. Here, the first subset of PRACH resources may be a set of qualifying resources (e.g., the set of qualifying resources 400) which has the metric greater than a first threshold value (e.g., the RSRP threshold).

At 620, the UE 602 may obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value. In one example, the first threshold value may be an RSRP threshold value, and the first subset of PRACH resources may be the set of qualifying resources (e.g., the set of qualifying resources 400) which has the metric greater than a first threshold value (e.g., the RSRP threshold). The UE 602 may determine the

In one aspect, the indication of the first subset of PRACH resources is obtained based on the set of channel metrics of the set of PRACH resources measured at 610. That is, based on the set of channel metrics of the set of PRACH resources measured at 610, the UE 602 may determine the first subset of the PRACH (e.g., the set of qualifying resources 400) that has the metric greater than a first threshold value (e.g., the RSRP threshold). 620 may include 622.

At 622, the UE 602 may receive the indication of the first threshold value of the first subset of PRACH resources from the network node 604. Here, the indication of the first threshold value may be received from the network node 604. That is, the network node 604 may configure the first threshold value for the UE 602, and the UE 602 may determine the first subset of the PRACH resources based on the first threshold value.

At 630, the UE 602 may select a first PRACH resource from the first subset of

PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource. The UE 602 may select the first PRACH resource (e.g., the RACH resource) for transmitting the RACH message at 640 based on a balanced analysis of a power usage on the UE's side and the time distance from the current time to the corresponding RO. 630 may include 632, 634, 636, and 638.

At 632, the UE 602 may identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources. Here, the second PRACH resource having the greatest set of channel metrics may be referred to as the best SSB/CSI-RS (or the strongest resource) among the first subset of PRACH resources (e.g., the set of qualifying resources 400).

At 634, the UE 602 may calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource. In one aspect, the first PRACH resource may be selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource.

At 636, the UE 602 may identify a second subset of PRACH resources from the first subset of PRACH resources, where each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value. That is, to reduce the power consumption impact on the UE's side, the UE 602 may filter down the first subset of PRACH resources (e.g., the set of qualifying resources 400) down to the second subset of PRACH resources (e.g., the cluster 410) based on the channel metric difference of each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource (e.g., the best SSB/CSI-RS). In one aspect, the first PRACH resource may be selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource. That is, the first RO associated with the first PRACH resource may have a smallest time difference from a current time in the second subset of PRACH resources, and the UE 602 may select the PRACH resource with the smallest time difference from the current time in the second subset of PRACH resources as the first PRACH resource (e.g., the RACH resource) to transmit the RACH message to the network node 604.

At 638, the UE 602 may determine that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value. That is, the UE 602 may compare each qualifying resource to the best resource, and determine all the qualifying resources have differences in power with respect to the best resource that is greater than the power threshold. The UE 602 may determine that that no qualifying resources meet the power threshold criterial. Accordingly, the UE 602 may select the second PRACH resource as the first PRACH resource.

At 640, the UE 602 may transmit a RACH message to a network node 604 in the first RO. The RACH message may include a PRACH preamble. That is, the RACH message may be the Msg1 including PRACH preamble, and the UE 602 may transmit the Msg1 including the PRACH preamble to the network node 604 using the first RO associated with the first PRACH resource (e.g., the RACH resource).

FIG. 7 is a flowchart 700 of a method of wireless communication. The method may be performed by a UE (e.g., the UE 104/602; the apparatus 904). The UE may evaluate the multiple qualifying SSBs/CSI-RSs and select one SSB/CSI-RS among the qualifying SSBs/CSI-RSs based on a scheduling opportunity of the associated ROs and a power usage on the UE side. The UE may obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO.

At 706, the UE may trigger a RACH procedure. The triggering of the RACH procedure may be based on various scenarios including initial access procedure, a radio link failure, etc. Based on triggering the RACH procedure, the UE may obtain a first subset of PRACH resources from a set of PRACH resources at 720. For example, at 606, the UE 602 may trigger a RACH procedure. Furthermore, 706 may be performed by a RACH resource selecting component 198.

At 708, the UE may receive a second indication of the second threshold value. Here, the second threshold value may be a power threshold for the UE to determine a second set of PRACH resources (e.g., a cluster 410) of PRACH resources that meets the power threshold, at 736. For example, at 608, the UE 602 may receive a second indication of the second threshold value. Furthermore, 708 may be performed by the RACH resource selecting component 198.

At 710, the UE may measure the set of channel metrics of the set of PRACH resources. In one example, the set of channel metrics of each PRACH resource of the first subset of PRACH resources may include an RSRP or an SNR of each PRACH resource of the first subset of PRACH resources. Here, the first subset of PRACH resources may be a set of qualifying resources (e.g., the set of qualifying resources 400) which has the metric greater than a first threshold value (e.g., the RSRP threshold). For example, at 610, the UE 602 may measure the set of channel metrics of the set of PRACH resources. Furthermore, 710 may be performed by the RACH resource selecting component 198.

At 720, the UE may obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value. For example, at 620, the UE 602 may obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value. Furthermore, 720 may be performed by the RACH resource selecting component 198.

At 722, the UE may receive the indication of the first threshold value of the first subset of PRACH resources from the network node 604. Here, the indication of the first threshold value may be received from the network node 604. That is, the network node 604 may configure the first threshold value for the UE 602, and the UE 602 may determine the first subset of the PRACH resources based on the first threshold value. For example, at 622, the UE 602 may receive the indication of the first threshold value of the first subset of PRACH resources from the network node 604. Furthermore, 722 may be performed by the RACH resource selecting component 198.

At 730, the UE may select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource. The UE may select the first PRACH resource (e.g., the RACH resource) for transmitting the RACH message at 640 based on a balanced analysis of a power usage on the UE's side and the time distance from the current time to the corresponding RO. For example, at 630, the UE 602 may select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource. Furthermore, 730 may be performed by the RACH resource selecting component 198. 730 may include 732, 734, 736, and 738.

At 732, the UE may identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources. Here, the second PRACH resource having the greatest set of channel metrics may be referred to as the best SSB/CSI-RS (or the strongest resource) among the first subset of PRACH resources (e.g., the set of qualifying resources 400). For example, at 632, the UE 602 may identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources. Furthermore, 732 may be performed by the RACH resource selecting component 198.

At 734, the UE may calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource. In one aspect, the first PRACH resource may be selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource. For example, at 634, the UE 602 may calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource. Furthermore, 734 may be performed by the RACH resource selecting component 198.

At 736, the UE may identify a second subset of PRACH resources from the first subset of PRACH resources, where each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value. That is, to reduce the power consumption impact on the UE's side, the UE may filter down the first subset of PRACH resources (e.g., the set of qualifying resources 400) down to the second subset of PRACH resources (e.g., the cluster 410) based on the channel metric difference of each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource (e.g., the best SSB/CSI-RS). In one aspect, the first PRACH resource may be selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource. That is, the first RO associated with the first PRACH resource may have a smallest time difference from a current time in the second subset of PRACH resources, and the UE may select the PRACH resource with the smallest time difference from the current time in the second subset of PRACH resources as the first PRACH resource (e.g., the RACH resource) to transmit the RACH message to the network node. For example, at 636, the UE 602 may identify a second subset of PRACH resources from the first subset of PRACH resources, where each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value. Furthermore, 736 may be performed by the RACH resource selecting component 198.

At 738, the UE may determine that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value. That is, the UE may compare each qualifying resource to the best resource, and determine all the qualifying resources have differences in power with respect to the best resource that is greater than the power threshold. The UE may determine that that no qualifying resources meet the power threshold criterial. Accordingly, the UE 602 may select the second PRACH resource as the first PRACH resource. For example, at 638, the UE 602 may determine that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value. Furthermore, 738 may be performed by the RACH resource selecting component 198.

At 740, the UE may transmit a RACH message to a network node in the first RO. The RACH message may include a PRACH preamble. That is, the RACH message may be the Msg1 including PRACH preamble, and the UE may transmit the Msg1 including the PRACH preamble to the network node using the first RO associated with the first PRACH resource (e.g., the RACH resource). For example, at 640, the UE 602 may transmit a RACH message to a network node 604 in the first RO. Furthermore, 740 may be performed by the RACH resource selecting component 198.

FIG. 8 is a flowchart 800 of a method of wireless communication. The method may be performed by a UE (e.g., the UE 104/602; the apparatus 904). The UE may evaluate the multiple qualifying SSBs/CSI-RSs and select one SSB/CSI-RS among the qualifying SSBs/CSI-RSs based on a scheduling opportunity of the associated ROs and a power usage on the UE side. The UE may obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO.

At 820, the UE may obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value. For example, at 620, the UE 602 may obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value. Furthermore, 820 may be performed by the RACH resource selecting component 198.

At 830, the UE may select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource. The UE may select the first PRACH resource (e.g., the RACH resource) for transmitting the RACH message at 640 based on a balanced analysis of a power usage on the UE's side and the time distance from the current time to the corresponding RO. For example, at 630, the UE 602 may select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource. Furthermore, 830 may be performed by the RACH resource selecting component 198.

At 840, the UE may transmit a RACH message to a network node in the first RO. The RACH message may include a PRACH preamble. That is, the RACH message may be the Msg1 including PRACH preamble, and the UE may transmit the Msg1 including the PRACH preamble to the network node using the first RO associated with the first PRACH resource (e.g., the RACH resource). For example, at 640, the UE 602 may transmit a RACH message to a network node 604 in the first RO. Furthermore, 840 may be performed by the RACH resource selecting component 198.

FIG. 9 is a diagram 900 illustrating an example of a hardware implementation for an apparatus 904. The apparatus 904 may be a UE, a component of a UE, or may implement UE functionality. In some aspects, the apparatus 904 may include a cellular baseband processor 924 (also referred to as a modem) coupled to one or more transceivers 922 (e.g., cellular RF transceiver). The cellular baseband processor 924 may include on-chip memory 924′. In some aspects, the apparatus 904 may further include one or more subscriber identity modules (SIM) cards 920 and an application processor 906 coupled to a secure digital (SD) card 908 and a screen 910. The application processor 906 may include on-chip memory 906′. In some aspects, the apparatus 904 may further include a Bluetooth module 912, a WLAN module 914, an SPS module 916 (e.g., GNSS module), one or more sensor modules 918 (e.g., barometric pressure sensor/altimeter; motion sensor such as inertial management unit (IMU), gyroscope, and/or accelerometer(s); light detection and ranging (LIDAR), radio assisted detection and ranging (RADAR), sound navigation and ranging (SONAR), magnetometer, audio and/or other technologies used for positioning), additional memory modules 926, a power supply 930, and/or a camera 932. The Bluetooth module 912, the WLAN module 914, and the SPS module 916 may include an on-chip transceiver (TRX) (or in some cases, just a receiver (RX)). The Bluetooth module 912, the WLAN module 914, and the SPS module 916 may include their own dedicated antennas and/or utilize the antennas 980 for communication. The cellular baseband processor 924 communicates through the transceiver(s) 922 via one or more antennas 980 with the UE 104 and/or with an RU associated with a network entity 902. The cellular baseband processor 924 and the application processor 906 may each include a computer-readable medium/memory 924′, 906′, respectively. The additional memory modules 926 may also be considered a computer-readable medium/memory. Each computer-readable medium/memory 924′, 906′, 926 may be non-transitory. The cellular baseband processor 924 and the application processor 906 are each responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the cellular baseband processor 924/application processor 906, causes the cellular baseband processor 924/application processor 906 to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the cellular baseband processor 924/application processor 906 when executing software. The cellular baseband processor 924/application processor 906 may be a component of the UE 350 and may include the memory 360 and/or at least one of the TX processor 368, the RX processor 356, and the controller/processor 359. In one configuration, the apparatus 904 may be a processor chip (modem and/or application) and include just the cellular baseband processor 924 and/or the application processor 906, and in another configuration, the apparatus 904 may be the entire UE (e.g., see 350 of FIG. 3 ) and include the additional modules of the apparatus 904.

As discussed supra, the RACH resource selecting the RACH resource selecting component 198 is configured to obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO. The RACH resource selecting component 198 may be within the cellular baseband processor 924, the application processor 906, or both the cellular baseband processor 924 and the application processor 906. The RACH resource selecting component 198 may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by one or more processors configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by one or more processors, or some combination thereof. As shown, the apparatus 904 may include a variety of components configured for various functions. In one configuration, the apparatus 904, and in particular the cellular baseband processor 924 and/or the application processor 906, includes means for obtaining an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, means for selecting a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and means for transmitting a RACH message to a network node in the first RO. In one configuration, the set of PRACH resources includes a set of SSBs or a set of CSI-RSs. In one configuration, the apparatus 904, and in particular the cellular baseband processor 924 and/or the application processor 906, further includes means for measuring the set of channel metrics of the set of PRACH resources, where the indication of the first subset of PRACH resources is obtained based on the set of channel metrics of the set of PRACH resources. In one configuration, the means for selecting the first PRACH resource from the first subset of PRACH resources is further configured to identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources, and calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource, where the first PRACH resource is selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource. In one configuration, the set of channel metrics of each PRACH resource of the first subset of PRACH resources includes an RSRP or an SNR of each PRACH resource of the first subset of PRACH resources. In one configuration, the means for selecting the first PRACH resource from the first subset of PRACH resources is further configured to identify a second subset of PRACH resources from the first subset of PRACH resources, where each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value, where the first PRACH resource is selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource. In one configuration, where the first RO associated with the first PRACH resource has a smallest time difference from a current time in the second subset of PRACH resources. In one configuration, the apparatus 904, and in particular the cellular baseband processor 924 and/or the application processor 906, includes further including means for receiving a second indication of the second threshold value. In one configuration, the means for selecting the first PRACH resource from the first subset of PRACH resources is further configured to determine that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value, where the second PRACH resource is selected as the first PRACH resource. In one configuration, the apparatus 904, and in particular the cellular baseband processor 924 and/or the application processor 906, includes means for triggering a RACH procedure, the first subset of PRACH resources being obtained based on the triggered RACH procedure. In one configuration, the means for obtaining the indication of the first subset of PRACH resources is further configured to receive the indication of the first threshold value of the first subset of PRACH resources from the network node. In one configuration, the RACH message includes a PRACH preamble. The means may be the component 198 of the apparatus 904 configured to perform the functions recited by the means. As described supra, the apparatus 904 may include the TX processor 368, the RX processor 356, and the controller/processor 359. As such, in one configuration, the means may be the TX processor 368, the RX processor 356, and/or the controller/processor 359 configured to perform the functions recited by the means.

According to the current disclosure, a UE may be configured to obtain an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmit a RACH message to a network node in the first RO. To select the first PRACH resource from the first subset of PRACH resources, the UE may identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources, calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource, and identify a second subset of PRACH resources from the first subset of PRACH resources, where each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value, where the first PRACH resource is selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource.

It is understood that the specific order or hierarchy of blocks in the processes/flowcharts disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes/flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not limited to the aspects described herein, but are to be accorded the full scope consistent with the language claims. Reference to an element in the singular does not mean “one and only one” unless specifically so stated, but rather “one or more.” Terms such as “if,” “when,” and “while” do not imply an immediate temporal relationship or reaction. That is, these phrases, e.g., “when,” do not imply an immediate action in response to or during the occurrence of an action, but simply imply that if a condition is met then an action will occur, but without requiring a specific or immediate time constraint for the action to occur. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. Sets should be interpreted as a set of elements where the elements number one or more. Accordingly, for a set of X, X would include one or more elements. If a first apparatus receives data from or transmits data to a second apparatus, the data may be received/transmitted directly between the first and second apparatuses, or indirectly between the first and second apparatuses through a set of apparatuses. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are encompassed by the claims. Moreover, nothing disclosed herein is dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module,” “mechanism,” “element,” “device,” and the like may not be a substitute for the word “means.” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”

As used herein, the phrase “based on” shall not be construed as a reference to a closed set of information, one or more conditions, one or more factors, or the like. In other words, the phrase “based on A” (where “A” may be information, a condition, a factor, or the like) shall be construed as “based at least on A” unless specifically recited differently.

The following aspects are illustrative only and may be combined with other aspects or teachings described herein, without limitation.

Aspect 1 is a method of wireless communication at a UE, including obtaining an indication of a first subset of PRACH resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value, selecting a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first RO associated with the first PRACH resource, and transmitting a RACH message to a network node in the first RO.

Aspect 2 is the method of aspect 1, where the set of PRACH resources includes a set of SSBs or a set of CSI-RSs.

Aspect 3 is the method of any of aspects 1 and 2, further including measuring the set of channel metrics of the set of PRACH resources, where the indication of the first subset of PRACH resources is obtained based on the set of channel metrics of the set of PRACH resources.

Aspect 4 is the method of any of aspects 1 to 3, where selecting the first PRACH resource from the first subset of PRACH resources further includes identifying a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources, and calculating a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource, where the first PRACH resource is selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource.

Aspect 5 is the method of aspect 4, where the set of channel metrics of each PRACH resource of the first subset of PRACH resources includes an RSRP or an SNR of each PRACH resource of the first subset of PRACH resources.

Aspect 6 is the method of any of aspects 4 and 5, where selecting the first PRACH resource from the first subset of PRACH resources further includes identifying a second subset of PRACH resources from the first subset of PRACH resources, where each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value, where the first PRACH resource is selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource.

Aspect 7 is the method of aspect 6, where the first RO associated with the first PRACH resource has a smallest time difference from a current time in the second subset of PRACH resources.

Aspect 8 is the method of any of aspects 6 and 7, further including receiving a second indication of the second threshold value.

Aspect 9 is the method of any of aspects 4, 5, 7, and 8, where selecting the first PRACH resource from the first subset of PRACH resources further includes determining that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value, where the second PRACH resource is selected as the first PRACH resource.

Aspect 10 is the method of any of aspects 1 to 9, further including triggering a RACH procedure, the first subset of PRACH resources being obtained based on the triggered RACH procedure.

Aspect 11 is the method of any of aspects 1 to 10, where obtaining the indication of the first subset of PRACH resources further includes receiving the indication of the first threshold value of the first subset of PRACH resources from the network node.

Aspect 12 is the method of any of aspects 1 to 11, wherein the RACH message includes a PRACH preamble.

Aspect 13 is an apparatus for wireless communication including at least one processor coupled to a memory and configured to implement any of aspects 1 to 12, further including a transceiver coupled to the at least one processor.

Aspect 14 is an apparatus for wireless communication including means for implementing any of aspects 1 to 12.

Aspect 15 is a non-transitory computer-readable medium storing computer executable code, where the code when executed by a processor causes the processor to implement any of aspects 1 to 12. 

What is claimed is:
 1. An apparatus for wireless communication at a user equipment (UE), comprising: a memory; and at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to: obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value; select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first random access channel (RACH) occasion (RO) associated with the first PRACH resource; and transmit a RACH message to a network node in the first RO.
 2. The apparatus of claim 1, wherein the set of PRACH resources includes a set of synchronization signal blocks (SSBs) or a set of channel status information (CSI) reference signals (CSI-RSs).
 3. The apparatus of claim 1, wherein the at least one processor is further configured to measure the set of channel metrics of the set of PRACH resources, wherein the indication of the first subset of PRACH resources is obtained based on the set of channel metrics of the set of PRACH resources.
 4. The apparatus of claim 1, wherein, to select the first PRACH resource from the first subset of PRACH resources, the at least one processor is configured to: identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources; and calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource, wherein the first PRACH resource is selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource.
 5. The apparatus of claim 4, wherein the set of channel metrics of each PRACH resource of the first subset of PRACH resources includes a reference signal received power (RSRP) or a signal-to-noise ratio (SNR) of each PRACH resource of the first subset of PRACH resources.
 6. The apparatus of claim 4, wherein, to select the first PRACH resource from the first subset of PRACH resources, the at least one processor is further configured to: identify a second subset of PRACH resources from the first subset of PRACH resources, wherein each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value, wherein the first PRACH resource is selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource.
 7. The apparatus of claim 6, wherein the first RO associated with the first PRACH resource has a smallest time difference from a current time in the second subset of PRACH resources.
 8. The apparatus of claim 6, wherein the at least one processor is further configured to receive a second indication of the second threshold value.
 9. The apparatus of claim 4, wherein, to select the first PRACH resource from the first subset of PRACH resources, the at least one processor is further configured to: determine that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value, wherein the second PRACH resource is selected as the first PRACH resource.
 10. The apparatus of claim 1, wherein the at least one processor is further configured to trigger a RACH procedure, the first subset of PRACH resources being obtained based on the triggered RACH procedure.
 11. The apparatus of claim 1, wherein to obtain the indication of the first subset of PRACH resources, the at least one processor is further configured to: receive the indication of the first threshold value of the first subset of PRACH resources from the network node.
 12. The apparatus of claim 1, wherein the RACH message includes a PRACH preamble.
 13. The apparatus of claim 1, further comprising at least one of an antenna or a transceiver coupled to the at least one processor.
 14. A method for wireless communication at a user equipment (UE), comprising: obtaining an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value; selecting a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first random access channel (RACH) occasion (RO) associated with the first PRACH resource; and transmitting a RACH message to a network node in the first RO.
 15. The method of claim 14, wherein the set of PRACH resources includes a set of synchronization signal blocks (SSBs) or a set of channel status information (CSI) reference signals (CSI-RSs).
 16. The method of claim 14, further comprising measuring the set of channel metrics of the set of PRACH resources, wherein the indication of the first subset of PRACH resources is obtained based on the set of channel metrics of the set of PRACH resources.
 17. The method of claim 14, wherein selecting the first PRACH resource from the first subset of PRACH resources further comprises: identifying a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources; and calculating a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource, wherein the first PRACH resource is selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource.
 18. The method of claim 17, wherein the set of channel metrics of each PRACH resource of the first subset of PRACH resources includes a reference signal received power (RSRP) or a signal-to-noise ratio (SNR) of each PRACH resource of the first subset of PRACH resources.
 19. The method of claim 17, wherein selecting the first PRACH resource from the first subset of PRACH resources further comprises: identifying a second subset of PRACH resources from the first subset of PRACH resources, wherein each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value, wherein the first PRACH resource is selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource.
 20. The method of claim 19, wherein the first RO associated with the first PRACH resource has a smallest time difference from a current time in the second subset of PRACH resources.
 21. The method of claim 19, further comprising receiving a second indication of the second threshold value.
 22. The method of claim 17, wherein selecting the first PRACH resource from the first subset of PRACH resources further comprises: determining that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value, wherein the second PRACH resource is selected as the first PRACH resource.
 23. The method of claim 14, further comprising triggering a RACH procedure, the first subset of PRACH resources being obtained based on the triggered RACH procedure.
 24. The method of claim 14, wherein obtaining the indication of the first subset of PRACH resources further comprises: receiving the indication of the first threshold value of the first subset of PRACH resources from the network node.
 25. The method of claim 14, wherein the RACH message includes a PRACH preamble.
 26. An apparatus for wireless communication at a user equipment (UE), comprising: means for obtaining an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value; means for selecting a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first random access channel (RACH) occasion (RO) associated with the first PRACH resource; and means for transmitting a RACH message to a network node in the first RO.
 27. The apparatus of claim 26, wherein the means for selecting the first PRACH resource from the first subset of PRACH resources is configured to: identify a second PRACH resource having a second set of channel metrics that is greatest from the first subset of PRACH resources; and calculate a channel metric difference for each PRACH resource of the first subset of PRACH resources with respect to the second PRACH resource, wherein the first PRACH resource is selected from the first subset of PRACH resources based on the first set of channel metrics of the first PRACH resource.
 28. The apparatus of claim 27, wherein the means for selecting of the first PRACH resource from the first subset of PRACH resources is further configured to: identify a second subset of PRACH resources from the first subset of PRACH resources, wherein each PRACH resource of the second subset of PRACH resources has the channel metric difference with the second PRACH resource less than or equal to a second threshold value, wherein the first PRACH resource is selected from the second subset of PRACH resources based on the first RO associated with the first PRACH resource.
 29. The apparatus of claim 27, wherein the means for selecting of the first PRACH resource from the first subset of PRACH resources is further configured to: determine that all of the first subset of PRACH resources have channel metric differences with the second PRACH resource greater than a second threshold value, wherein the second PRACH resource is selected as the first PRACH resource.
 30. A computer-readable medium storing computer executable code at a user equipment (UE), the code when executed by a processor causes the processor to: obtain an indication of a first subset of physical random access channel (PRACH) resources in a set of PRACH resources, the first subset of PRACH resources having a set of channel metrics that is greater than or equal to a first threshold value; select a first PRACH resource from the first subset of PRACH resources based on a first set of channel metrics of the first PRACH resource or a first random access channel (RACH) occasion (RO) associated with the first PRACH resource; and transmit a RACH message to a network node in the first RO. 